Heat canola oil in a saute pan and cook onions over medium heat until they caramelize . Heat grill. Form ground beef into 8 (2-inch) patties. Season with garlic powder, salt, and pepper, and grill burgers until medium rare, remove to a platter and top with cheddar cheese slices to allow melting. Use a 2-inch circle cutter (or biscuit cutter) to cut the potato rolls into circles. Place burgers in rolls and top burgers with caramelized onion.